I am renting a place where the only air conditioner is a window unit mounted in the wall in the main living area. The space in that main room is about 325 sq ft, and it has a 9 ft ceiling on average. The unit is a Frigidaire FAS182H2A1. It looks like it was manufactured in 1999, but I can't recognize any other useful specs on the partially worn labels. So, I don't know what its BTU rating is, and I couldn't seem to find the manual online.

Earlier in the spring, I felt it wasn't cooling well, and I took off the front panel to see that it was caked with about 1/8" of dust and pet hair from previous tenants. The landlord removed this, but the aluminum fins were still clogged with gunk. I tried the only thing that our local Home Depot had for this which was an aerosol can of foaming cleaner, so I sprayed and scrubbed for a couple days. It looks a lot better, but I am not certain the fins are really cleaned out. The air conditioner is still occasionally spitting out what looks like chunks of dried black gunk that has been displaced from between the fins.

Last week it was about 95 degrees F outside, and after several hours of this thing being turned on to its max level, the room cooled down to about 81 degrees (with all doors to other rooms closed). I used a thermometer I had to measure the temperature of the air coming out of the unit, which was between 67 and 68 degrees.

It's only getting hotter outside (ugh), so I'd like to try to do something about this. So, here are my actual questions:

Just for clarification, there are two sets of fins. The inside ones and the outside ones. The outside ones will get caked with pollen, dust, dirt, bugs, etc and form a matte blocking air flow around the fins. Depending on where you live and how much the AC runs, you may need to clean this yearly. The best way is to open up the entire case and then get in there with water degreaser and a toothbrush to get all the gunk out.

Also, as Philip points out, that's a LOT Of BTUs for a very small space. If a unit is oversized, what will happen is that it will cool the space before it can dehumidify the space. So you end up with cold and damp...likely not something you want.

I'd second Philip and just go spend a few hundred bucks on a small 8000 btu unit.

Thanks... well, I would prefer that it cools the entire space, which is about 1000 sq ft. I typically keep all the doors open and the ceiling fans on in order to get better circulation.
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Chris FarmerJun 29 '12 at 21:57

I just read it was made in '99. THat's a pretty old window unit. Not sure I'd put too much effort into working on it, but you could have a Sears tech come out to clean/recharge it if you wanted to.
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DA01Jun 29 '12 at 22:14

Also, if you do end up replacing it (or your landlord does) you might want to consider two 10k btu units rather than one large 18k one. It'd be more efficient in cooling a divided space (not to mention easier to take in and out each season)
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DA01Jun 29 '12 at 22:15

Make sure the fins have not been mashed together so air can get in. If so brush the fins lightly with a brass wire brush.
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lqlarryJun 30 '12 at 0:38